Contact lenses made from silicone materials can generally be subdivided into two major classes, namely hydrogels and non-hydrogels. Non-hydrogels do not absorb appreciable amounts of water; whereas, hydrogels can absorb and retain water in an equilibrium state. Hydrogels generally have a water content greater than about ten weight percent and more commonly between about fifteen to about eighty weight percent.
Silicone contact lenses may tend to have relatively hydrophobic, non-wettable surfaces. Thus, various publications disclose methods for rendering the surface of silicone contact lenses more hydrophilic to improve their biocompatibility or wettability by tear fluid in the eye. Examples include U.S. Pat. Nos. 6,193,369; 4,143,949; 5,135,297; 5,726,733; 6,550,915; 6,213,604; 6,348,507; 6,630,243; 6,428,839; 6,200,626; 6,440,571; 6,599,559; 4,055,378; 4,122,942; 4,214,014; U.S. Pat. Nos. 4,143,949; 4,632,844; 4,312,575; 5,326,584; 4,312,575; U.S. Pat. Nos. 4,632,844; 6,638,563; and 5,760,100; WO 01/34312; WO 04/060431; WO 95/04609 and US 2005-0045589. Examples of commercial silicone hydrogel contact lenses include: balafilcon A contact lenses, which include plasma-oxidized silicate surfaces; and lotrafilcon A contact lenses, which include plasma-deposited hydrocarbon coating surfaces.
It is important for contact lenses to be comfortable during wear. Also, it is important to avoid corneal edema, inflammation and other adverse effects resulting from contact lens wear, especially lenses intended for wearing for an extended period of time. Finally, in the case of contact lenses having a modified surface, it is important for the modified surface to be optically clear and able to withstand manufacturing process conditions such as hydration and autoclaving for sterilization, as well as cleaning or disinfection treatments performed by the contact lens wearer.